Barometers commonly have indexes settable independently of the barometer for showing direction of barometric pressure change. In the prior art such indexes have been incorporated in or mounted on the crystal of the barometer case for setting either by rotating the crystal or the pointer.
It is the general object of the present invention to provide an improved form of barometer wherein the barometer pressure change direction indicator is set by rotating the barometer crystal. A particular object of the invention is to provide a new and improved manner of mounting the crystal for rotation whereby the crystal is freely-rotatable yet effectively not removable, except by means of a special tool.